Aluminoxanes are generally prepared by the hydrolysis of aluminum alkyls either by direct water addition or by treatment with salt hydrates. Aluminoxanes are used in combination with various types of metallocenes and/or transition metal compounds to catalyze olefin oligomerization and polymerization. These catalyst components can be supported on solid carriers such as metal oxides, for example silica or alumina, for use in heterogeneous and gas phase polymerizations.

Methylaluminoxane (MAO) is the most useful of all aluminoxanes for polymeriza- tion applications. However, certain limitations are associated with regular methyl- aluminoxane solutions. Such limitations include poor solubility, especially in aliphatic solvents, instability, and gel formation.

The present invention relates to the alleviation of most if not all of the present problems associated with the industrial use of methylaluminoxanes as co-catalyst components.

The reactions of trialkylaluminums with M-X species to produce the liquid clathrate phenomenon have been described by such authors as Atwood (Coordination Chemistry of Aluminum, VCH Publishers, Inc. 1993, p. 197), Robinson (Coordination Chemistry Reviews, 1992, 112, p. 227) and Sangokoya (J. Incl. Phenom., 1988, 6, p.

263).

U.S. Patent No. 5,565,395 describes the formation of aluminoxanate compositions which are the reaction products of aluminoxanes, such as methylaluminoxane, and certain salts of polyoxy-compounds such as sodium aluminate and lithium silicate. These materials are obtained by the formation of only a transient liquid clathrate which quickly turns to solid aluminoxane compositions described as aluminoxanates.

EP 0 755 936 A2, published January 29, 1997, describes siloxy-aluminoxane compositions which contain hydrocarbylsiloxane moieties which are substantially free of Si-OH bonds, in which the molar portion of aluminum to hydrocarbylsiloxane is from 1:1 to 1000:1.

The present invention forms stable, liquid clathrate aluminoxane compositions.

The stable, liquid clathrate aluminoxane compositions show remarkable solubility and stability with no sign. of gel formation even at higher concentrations than commercially available methylaluminoxane solutions. This permits the shipment and storage and use of concentrated (30 to 60 weight percent) MAO solutions.

In accordance with the invention there is provided a stable, liquid clathrate composition which comprises the reaction product, in an aromatic solvent, of an aluminoxane and an organosilicon compound, a hydrocarbyloxysilane, which is effective to form a stable, liquid clathrate composition with said aluminoxane.

The hydrocarbyloxysilanes have the formula: (RO)4 nRnSi where R is, independently, hydrocarbyl having up to about 18 carbon atoms (e.g., alkyl, cycloalkyl, aryl, aralkyl) and n is 0 to 3; and hydrocarbylpolysiloxanes having from 2 to 6 silicon atoms in the molecule and which are separated from each other by an oxygen atom such that there is a linear, branched or cyclic backbone of alternating Si and oxygen atoms, with the remainder of the four valence bonds of each of the silicon atoms individually satisfied by a univalent hydrocarbyl group, R, as just defined. Preferred hydrocarbyl groups, R, are methyl, ethyl and phenyl. Examples of such organosilicon compounds include tetramethoxysilane, tetraethoxysilane, tetraphenoxysilane, methoxytrimethylsilane, ethoxytrimethylsilane, hexamethyldisiloxane, hexaethyldi- siloxane, hexaphenyldisiloxane, tetramethyldiphenyldisiloxane, dimethyltetraphenyl- disiloxane, hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, octaphenylcyclo- tetrasiloxane, octamethyltrisiloxane, decamethyltetrasiloxane, dodecamethylpentasiloxane, and tetradecamethylhexasiloxane.

Also provided is a process for preparing a methylaluminoxane composition which is substantially free of trimethylaluminum comprising (a) reacting a solution of methylaluminoxane, which contains a trimethylaluminum component, in an aromatic solvent with a hydrocarbyloxysilane which is effective to form a stable liquid clathrate composition with said methylaluminoxane so as to form a lower liquid methyl- aluminoxane containing clathrate layer and an upper, aromatic solvent layer which contains said trimethylaluminum component, and (b) separating said clathrate layer from said aromatic solvent layer.

Further, there is provided particulate solid aluminoxane-hydrocarbyloxysilane compositions obtained by removal of the aromatic inclusion solvent from the dense lower liquid layer of the liquid clathrate composition. Also, in accordance with the present invention polymerization catalyst systems are prepared using either the liquid clathrate compositions or the particulate solid aluminoxane-hydrocarbyloxysilane compositions, which can optionally be supported on solid carriers, in combination with co-catalysts such as metallocenes or transition or lanthanide metal compounds such as Ziegler/Natta type catalysts.

Conventional methylaluminoxane solutions can be vacuum stripped to obtain solid methylaluminoxane. It is believed that this material exhibits fouling problems in slurry or particle form polymerization due to the presence of a significant amount of soluble aluminum compounds. The inventive solid aluminoxane-hydrocarbyloxysilane compositions are virtually insoluble in aliphatic hydrocarbons and thus offer significant improvements with respect to reactor fouling.

Hydrocarbylaluminoxanes may exist in the form of linear or cyclic polymers with the simplest monomeric compounds being a tetraalkylaluminoxane such as tetramethyl- aluminoxane, (CH3)2AlOAl(CH3)2, or tetraethylaluminoxane, (C2H^)2AlOAl(C2Hs)2. The compounds preferred for use in olefin polymerization catalysts are oligomeric materials, sometimes referred to as polyalkylaluminoxanes, which usually contain 4 to 20 of the repeating units: where R is Cl-C,0 alkyl and is preferably methyl. The exact structure of aluminoxanes has not been defined and they may contain linear, cyclic and/or cross-linked species.

Methyl-aluminoxanes (MAOs) normally have lower solubility in organic solvents than higher alkylaluminoxanes and the methylaluminoxane solutions tend to be cloudy or gelatinous due to the separation of particles and agglomerates. In order to improve the solubility of the methylaluminoxane, higher alkyl groups, e.g. C2 to C20 can be included such as by hydrolyzing a mixture of trimethylaluminum with a ¼ to C20 alkylaluminum compound such as, for example, triethyl-aluminum, tri-n-propylaluminum, triisobutylalu-

minum, tri-n-hexylaluminum, tri-n-octylaluminum or a triarylaluminum. Such mixed methyl-higher alkyl or aryl aluminoxanes are included in the term "methylaluminoxane" as used herein. Such modified methylaluminoxanes are described, for example, in U.S.

Patent No. 5,157,008. Besides MAO, non-limiting examples of hydrocarbyl- aluminoxanes for use in the invention include ethylaluminoxanes (EAO), isobutylalumin- oxanes (IBAO), n-propylaluminoxanes, n-octylaluminoxanes, and phenylaluminoxanes.

The hydrocarbylaluminoxanes can also contain up to about 20 mole percent (based on aluminum) of moieties derived from amines, alcohols, ethers, esters, phosphoric and carboxylic acids, thiols, aryl disiloxanes, and alkyl disiloxanes to further improve activi- ty, solubility and/or stability.

The aluminoxanes can be prepared as known in the art by the partial hydrolysis of hydrocarbylaluminum compounds. Any hydrocarbylaluminum compound or mixture of compounds capable of reacting with water to form an aluminoxane can be used. This includes, for example, trialkylaluminum, triarylaluminum, and mixed alkyl aryl aluminum. The hydrocarbylaluminum compounds can be hydrolyzed by adding either free water or water containing solids, which can be either hydrates or porous materials which have absorbed water. Because it is difficult to control the reaction by adding water per se, even with vigorous agitation of the mixture, the free water is preferably added in the form of a solution or a dispersion in an organic solvent. Suitable hydrates include salt <BR> <BR> <BR> hydrates such as, for example, CuSO4#5H2O, Al2(SO4)3#18H2O, FeSO4#7H2O,<BR> <BR> <BR> <BR> <BR> AlCl3#6H2O, Al(NO3)3#9H2O, MgSO4#7H2O,MgCl2#6H2O, ZnSO4#7H2O,<BR> <BR> <BR> <BR> <BR> Na2SO4#10H2O, Na3PO4#12H2O, LiBr#2H2O, LiCl#1H2O, LiI#2H2O, LiI#3H2O, KF#2H2O, and NaBre2H20, and alkali or alkaline earth metal hydroxide hydrates such as, for example, NaOH#H2O, NaOHe2H2O, Ba(OH)2C8H2O, KOH.2112O, CsOH#1H2O, and LiOH lH2O. Mixtures of any of the above hydrates can be used.

The mole ratios of free water or water in the hydrate or in porous materials such as alumina or silica to total alkyl aluminum compounds in the mixture can vary widely, such as for example from 2:1 to 1:4 with ratios of from 4:3 to 1:3.5 being preferred.

Such hydrocarbylaluminoxanes and processes for preparing hydrocarbylalu- minoxanes are described, for example, in U.S. Patent Nos. 4,908,463; 4,924,018; 5,003,095; 5,041,583; 5,066,631; 5,099,050; 5,157,008; 5,157,137; 5,235,081;

5,248,801, and 5,371,260. The methylaluminoxanes contain varying amounts, of from 5 to 35 mole percent, of the aluminum value as unreacted trimethylaluminum (TMA).

The process of the invention removes most of this unreacted trimethylaluminum which can be recovered and re-used in making additional methylaluminoxane.

The novel, liquid clathrate aluminoxane compositions are prepared by the reaction of the aluminoxanes, especially methylaluminoxane, with hydrocarbyloxysilanes. Such reactions are characterized by the formation of two stable immiscible organic layers when carried out in an aromatic solvent. The appearance of the immiscible layers is termed liquid clathrate formation.

By analysis, the upper solvent layer consists mainly of TMA and toluene, while the lower liquid clathrate layer contains mainly MAO-hydrocarbyloxysilane and toluene with almost no titratable TMA content as shown by pyridine titration. This lower layer represents the stable, liquid clathrate aluminoxane composition embodiment of the invention.

Non-limiting examples of suitable aromatic solvents include, toluene, benzene, xylenes, ethylbenzene, cumene, mesitylene, and cymene. The preferred solvent is toluene.

The clathrate forming compounds are preferably added in excess to the amount that dissolves to form the clathrate with the extra amount being easily removed, such as by filtration. About stoichiometric or lesser amounts are effective to form stable clathrates, depending upon the compound. Preferably, amounts of from 0.01 to 0.5 moles of compound per mole of aluminum in the aluminoxane composition are added and more preferably from 0.05 to 0.2 moles. The starting concentration of aluminoxane in solvent is not particularly critical and usually ranges from 5 to 30 weight percent solution.

As described herein, the weight percent of aluminoxane in the solutions is based on the total weight of aluminoxane and any unreacted trialkylaluminum in the solution. An advantage of the clathrates of the invention is that commercial MAO solutions are usually available as 5-20 wt. percent solutions in toluene. At higher concentrations, the inevitable limitations associated with solubility, stability and gel formation become extremely pronounced. Consequently, the transportation costs of the less concentrated solutions, especially to distant overseas places, significantly increase catalyst cost which

in turn will push up polymer cost. In contrast, the inventive liquid clathrate aluminoxane-hydrocarbyloxysilane compositions can contain MAO in high concentrations, e.g. 30-60 wt. percent depending on the nature of the hydrocar- byloxysilane. Furthermore, even at these high concentrations, the inventive liquid clathrate MAO-hydrocarbyloxysilane compositions are appreciably much more stable with respect to solubility, stability and gel formation compared to conventional MAO solutions.

The reaction temperature is chosen to provide a stable, liquid clathrate. By a stable liquid clathrate is meant that the two immiscible liquid layer systems remain intact such that the upper solvent layer can be separated from the lower clathrate layer.

Although the use of ambient temperatures is most convenient (i.e. from 15 to 300C), some compounds require elevated temperatures of up to 80"C or higher in order to form a stable, liquid clathrate. A suitable temperature for any particular compound can be experimentally determined.

Removal of solvent from the dense lower liquid clathrate layer such as by vacuum distillation or the addition of excess non-aromatic solvent results in the isolation of solid, particulate aluminoxane-hydrocarbyloxysilane compositions. The solid, particulate MAO-hydrocarbyloxysilane compositions are virtually insoluble in aliphatic hydro- carbons. When introduced into aromatic solvents, the novel MAO-hydrocarbyloxysilane composition will incorporate as much solvent as required to reform a liquid clathrate (inclusion solvent) which separates out from the rest of the solvent resulting again in two immiscible liquid layers.

The aluminoxane-hydrocarbyloxysilane composition can be used in combination with metallocenes and/or transition metal compounds to provide olefin polymerization catalysts.

A notable result of liquid clathrate formation is that the aluminoxane-hydrocar- byloxysilane product contains essentially no trimethylaluminum as indicated by pyridine titration. It should also be noted that the variability in trimethylaluminum content of methylaluminoxane is probably the major source of inconsistency in previously known supported catalyst systems. Therefore, this invention provides a means to avoid this inconsistency.

As used in this application, the term "metallocene" includes metal derivatives which contain at least one cyclopentadienyl moiety. Suitable metallocenes are well known in the art include the metallocenes of Groups 3, 4, 5, 6, lanthanide and actinide metals, for example, the metallocenes which are described in U.S. Patent Nos.

2,864,843; 2,983,740; 4,665,046; 4,874,880; 4,892,851; 4,931,417; 4,952,713; 5,017,714; 5,026,798; 5,036,034; 5,064,802; 5,081,231; 5,145,819; 5,162,278; 5,245,019; 5,268,495; 5,276,208; 5,304,523; 5,324,800; 5,329,031; 5,329,033; 5,330,948, 5,347,025; 5,347,026; and 5,347,752.

Non-limiting illustrative examples of such metallocenes are bis(cyclopentadienyl) zirconium dimethyl, bis(cyclopentadienyl)zirconium dichloride, bis(cyclopentadien- yl)zirconium monomethylmonochioride, bis(cyclopentadienyl)titanium dichloride, bis- (cyclopentadienyl)titanium difluoride, cyclopentadienylzirconium tri-(2-ethylhexanoate), bis(cyclopentadienyl)zirconium hydrogen chloride, bis(cyclopentadienyl)hafnium dichlo- ride, racemic and meso dimethylsilanylenebis(methylcyclopentadienyl)hafnium dichloride, racemic dimethylsilanylene-bis(indenyl)hafnium dichloride, racemic ethylene-bis(in- denyl)zirconium dichloride, (P5-indenyl)hafnium trichloride, (rlS-C,Me,)hafnium trichlo- ride, racemic dimethylsilanylenebis(indenyl)thorium dichloride, racemic dimethylsilan- ylenebis(4,7-dimethyl-1-indenyl)zirconium dichloride, racemic dimethylsilanylene-bis(in- denyl)uranium dichloride, racemic dimethylsilanylene-bis (2,3,5 -trimethyl- 1 -cyclopenta- dienyl)zirconium dichloride, racemic dimethylsilanylene(3 -methylcyclopentadienyl)- hafnium dichloride, racemic dimethylsilanylene-bis(1-(2-methyl-4-ethylindenyl zirconium dichloride; racemic dimethylsilanylene-bis(2-methyl4 ,5,6, 7-tetrahydro- I -indenyl) zirco- nium dichloride, bis(pentamethylcyclopentadienyl)thorium dichloride, bis(pentamethyl- cyclopentadienyl)uranium dichloride, (tert-butylamido)dimethyl(tetramethyl-n5-cyclo- pentadienyl)silanetitanium dichloride, (tert-butylamido)dimethyl(tetramethyl-P5-cyclo- pentadienyl)silanechromium dichloride, (tert-butylamido)dimethyl(-n5-cyclopentadienyl)- silanetitanium dichloride, (tert-butylamido)dimethyl(tetramethyl-P5-cyclopentadienyl)- silanemethyltitanium bromide, (tert-butylamido)(tetramethyl-P5-cyclopenta-dienyl)- 1,2- ethanediyluranium dichloride, (tert-butylamido)(tetramethyl-n5-cyclopenta-dienyl)-1,2- ethanediyltitanium dichloride, (methylamido)(tetramethyl-P5-cyclopenta-dienyl)-1,2- ethanediylcerium dichloride, (methylamido)(tetramethyl-n5-cyclopentadienyl)-1,2-

ethanediyl titanium dichloride, (ethylamido)(tetramethyl-P5-cyclopentadienyl)-methylene- titanium dichloride, (tert-butylamido)dibenzyl(tetramethyl-rl5-cyclopentadienyl)s ilane- benzyl vanadium chloride, (benzylamido)dimethyl(indenyl)silanetitanium dichloride, and <BR> <BR> <BR> (phenylphosphido)dimethyl(tetramethyl-P5-cyclopentadienyl)si lanebenzyltitanium chloride.

Suitable transition metal or lanthanide compounds include the well known Ziegler- Natta catalyst compounds of Group 4-6 metals. Non-limiting illustrative examples of such compounds include TiC14, TiBr4, Ti(OC2Hs)3Cl, Ti(OC2Hs)Cl3, Ti(OC4Hg)3Cl, Ti(OC3H7)2Cl2, Ti(OCl7)2Br2, VCl4, VOC13 VO(OC2115)3, ZrCl4, ZrCl3(OC2H5), Zr(OC2115)4, and ZrCl(OC4Hg)3.

The molar proportions of metallocene and/or transition metal or lanthanide compound in the catalyst composition to the aluminum derived from the aluminoxane in the aluminoxane-hydrocarbyloxysilane composition are selected to provide the desired degree of polymerization activity and generally range from 1 X 101 to 1 X 104 to 1 and preferably from 2 X 10l to 5 X 104 to 1.

Either the liquid clathiates or the solid aluminoxane-hydrocarbyloxysilane compositions can be used to prepare catalysts.

The metallocenes or transition or lanthanide compounds can be supported on the novel aluminoxane compositions. Also, the reaction of MAO-hydrocarbyloxysilane compositions with metallocene could be carried out in the presence of other organic or inorganic substrates such as silica, alumina and other support substrates which are known in the art as suitable support materials. The aluminoxane-hydrocarbyloxysilane composition can be initially reacted with the metallocenes and then with the support substrate or the aluminoxane-hydrocarbyloxysilane compositions can be reacted with the support substrate and then with the metallocenes, and vice versa. In addition, the original aluminoxane compound can be initially modified by treatment with an R3Al compound or mixtures thereof or treated with other reagents which do not result in an appreciable deterioration of the polymerization capability of the aluminoxane before being treated with the hydrocarbyloxysilane in order to form the aluminoxane-hydrocarbyloxysilane clathrate compositions.

The catalysts are effective to produce olefin polymers and especially ethylene

polymers, propylene polymers and ethylene/a-olefin copolymers. Examples of olefins that can be polymerized in the presence of the catalysts of the invention include a-olefins having 2 to 20 carbon atoms such as ethylene, propylene, l-butene, 1-hexene, 4-methyl- 1-pentene, l-octene, 1-decene, 1-dodecene, 1-tetradecene, l-hexadecene, and l-octa- decene. Polymerization of ethylene or copolymerization with ethylene and an a-olefin having 3 to 10 carbon atoms is preferable. Such polymerizations may be performed in either the gas or liquid phase (e.g. in a solvent, such as toluene, or in a diluent, such as heptane). The polymerization can be conducted at conventional temperatures (e.g., 0° to 250"C) and pressures (e.g., ambient to 50 kg/crr0) using conventional procedures as to molecular weight regulation.

The invention is further illustrated by, but is not intended to be limited to, the following examples of the clathrates of this invention useful in formation of polymerization catalysts of the types described above, both supported and unsupported.

All experiments were performed under inert atmosphere condition. Schlenk vacuum line and glasswares, in conjunction with dry N2-box were employed to handle all air sensitive materials. Reagents were obtained from commercial sources without further purification. Aluminoxane samples were obtained from stock solutions produced by Albemarle Corporation. Solvents were dried and distilled by standard methods.

Example 1 This example illustrates the use of a linear polysiloxane reagent (trisiloxane) to make aluminoxane liquid clathrate. A 30% MAO solution in toluene (128g, 652.8 mmol Al) was placed in a reaction bottle. Octamethyltrisiloxane (OMTS) was added (7.7g, 32.6 mmol, 5%). The mixture was stirred at room temperature for about one hour.

Two-layer formation was observed. The initial cloudy MAO solution became clear. The lower layer was clear, but denser than the top layer. H-1 NMR showed that the upper layer is composed mainiy of TMA and TMA reaction products.

Example 2 Decamethyltetrasiloxane (DMTS), which is also a linear polysiloxane, was used to form aluminoxane liquid clathrate compositions. Thus a 30% MAO solution in toluene (64g, 320 mmol Al) was treated with DMTS (4.97g, 16 mmol, 5%). Two clear liquid phases were obtained after stirring at room temperature for about two hours. H-1 NMR

showed that most of the original MAO structure remained in the thicker lower phase.

Example 3 Since most of the MAO structure appears to be in the lower layer, an attempt was made to see if it was possible to obtain new solid MAO compositions from the lower layer. Thus a 30% MAO solution (hereinafter "MAO 30 / TOL") (67g, 335 mmol Al) was allowed to react with DMTS (10.4g, 33.5 mmol, 10%). The mixture was stirred at room temperature for about eight hours. Two layers were formed. The lower layer was so thick that the magnetic stirrer stopped. The upper layer was decanted. Then hexane was added to the lower layer to give a slurry. After heating at 800C for about two hours, the slurry was filtered to obtain a new solid MAO composition. An attempt to take an NMR determination in CDCl3 showed vigorous reactivity of the solid with this solvent.

The solid initially gave a clear solution in TllF (d-8), but slowly over time developed precipitates.

Example 4 Cyclic polysiloxane, octamethylcyclotetrasiloxane (OMCTS) was also used to form aluminoxane liquid clathrate compositions. MAO 30 / TOL (32g, 163.2 mmol Al) was treated with OMCTS (12.lug, 40.8 mmol, 25%). The mixture was stirred at room temperature for about two hours to obtain two liquid layer phases. The two phases were separated using a separating funnel inside a dry box. Both phases remained clear without solid precipitation for over six months.

Example 5 Advantage was taken of using an aluminoxane liquid clathrate composition to make solid catalyst systems containing metallocene without the usual difficulties associated with use of a silica support. Thus, solid MAO was obtained by treating MAO 30 / TOL (131.6g, 661.9 mmol Al) with DMTS (20.6g, 66.2 mmol, 10%). Two- layer product was formed. After stirring overnight at room temperature, the lower layer became very thick. The top layer was easily decanted. The bottom layer was treated with hexane to obtain solid product. Drying under reduced pressure afforded 40g of solid product.

The solid product (6.3g, 86.3 mmol Al) was then treated with a zirconocene dichloride (0.2327g, 0.5754 mmol) in a slurry of heptane. The colorless slurry slowly

turned yellowish-red while stirring overnight at room temperature. The slurry was filtered and washed several times with hexane. Yellow-orange solid (5.4g) product was obtained after vacuum drying. This product was shown to be very active in ethylene polymerization.

Example 6 Methoxytrimethylsilane (MTMS) was also used to obtain aluminoxane liquid clathrate composition. However, a large amount of MTMS was necessary to form the clathrate. Thus, MAO 30 / TOL (27.4g, 137.8 mmol Al) was treated with MTMS (14.4g, 137.8 mmol, 1:1 molar). After stirring at room temperature for about two hours, liquid clathrate resulted. The mixture was then left stirring at room temperature for greater than four weeks, while the liquid clathrate persisted. The mixture was separated and both liquid layers showed no solid precipitation for several months.

Example 7 Another type of organosilicon compound, tetraalkoxysilane, was used to produce the liquid clathrate phenomenon effect on methylaluminoxane. A solution of MAO in toluene (63g, 315 mmol Al) was allowed to react with tetraethoxysilane (6.6g, 31.5 mmol, 10%). After stirring for one hour at room temperature, an aluminoxane liquid clathrate composition was observed. Stirring at room temperature for another 60 hours, the liquid clathrate persisted.

In almost all of the examples, it appears that there is a fixed minimum amount of a particular reagent to initiate the formation of liquid clathrate. Below this set limit, a clear one phase liquid solution is obtained. It is also surprising that in most cases the MAO can support a relatively large amount of organosilicon reagent and still maintain high polymerization activity. Ordinarily, most additives to MAO solution have the potential of causing deactivation in polymerization.

By "stable" as used herein is meant that the clathrate composition formed as described herein when stored in the dark at 25"C in an anhydrous, inert atmosphere will remain essentially unchanged for at least 720 hours (30 days).